Electric-arc lamp.



No. 635,545. Patented Oct. 24, I899. D. HIGHAM.

ELECTRIC ARC LAMP.

(Applicatiun filed Apr. 29, 1899.) (No Model.) J

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UNITED STATES PATENT Fries.

DANIEL I-IIGHAM, OF CAMBRIDGE, MASSACHUSETTS.

ELECTRIC-ARC LAM P.

SPECIFICATION forming part of Letters Patent No. 635,545, dated October 24, 1899.

Application filed April 29, 1899. Serial No. 715,018. (No modelJ To a whom, it may concern:

Be it known that I, DANIEL HIGHAM, a citizen of the United States of America, residing in Cambridge, county of Middlesex, State of Massachusetts, have invented Improvements in Arc-Lamps, of which the following is a specification.

This invention relates to electric-arc lamps for use more particularly on direct-current constant-potential circuits, and has for its object to effect a saving in the amount of electrical energy consumed in the dead resistance now generally used in connection with such lamps for obtaining stability of the current. In my Patent No. 510,260 I have shown means for effecting a saving in the amount of electrical energy so consumed; butthe method of operation therein described consists of varying the length of the arc, and could not therefore effect an absolute condition of stability of current-t1] at is, could not eifect stability with a fixed length of arc whereas the dead-resistance means new generally used in connection with direct-current constant-potential arc-lamps will effect an absolute condition of stability-that is, will effect stability with a fixed length of are.

Now it is the object of the present invention to effect absolute stability in the sense herein conveyed, while at the same time effecting all the saving of electrical energy that could be obtained by a method requiring continual variation in the length of the are.

The operation of the present invention will be best understood after pointing out the underlying conditions of instability of the electric arc and the manner in which those conditions are now met by the use of the dead resistance. If an inclosed electric are be formed between two electrodes and supplied with current under control of a suitable handrheostat in the arc-circuit, it will be found, when the currentis adjusted to, say, five amperes, and the electrodes set at a position for a difference of potential at the are of eighty volts, that an adjustment of current to four amperes without changing theposition of the electrodes will cause a rise of potential at the arc to about eighty-five volts, or if the current be adjusted to six amperes with the same position of the electrodes (for five amperes and eighty volts potential at the arc) the potential at the arc will be found to fall to about seventy-five volts. From this it will be seen why it is an impossibility to supply such an arc with a constant potential at its electrodes and have a stable condition of current, for a constant potential of eighty volts supplied at the electrodes would not be sufficient to sustain a fall of current and would be too much for a rise of current. Therefore to obtain stability of current for such an are its electrodes must be supplied with a varying potential to meet the requirements of the arc that is, the potential supplied to its electrodes should be made to vary inversely with and in such a definite relation in amount to variations of current passing as to cause the potential supplied at the arc to rise slightly above eighty-five volt-s when the current falls to four amperes, so as to be sufficient to sustain that fall of current, and should fall slightly below seventy-five volt-s when the current rises to six amperes, so as to be sufficient to sustain that rise of current. Hence if the potential were made to vary proportionately for intermediate variations of current a stable condition of current must result independently of variation in length of the are. In a five-ampere inclosed arc-lamp for direct current one hundred and ten volt constant-potential circuits this inverse varying supply of potential at the arc in relation to variation of currents is accomplished by placing in the arc-circuit about six ohms of dead resistance to normally take up a drop of potential of about thirty volts, leaving "eighty volts potential at the are, so that if the current falls to four amperes there would only be twenty-four volts drop of potential by the six ohms of dead resistance, which with a constant potential at the main of one hundred and ten volts would cause a rise of potential at the arc to eighty-six volts, and if the current should rise to six amperes the drop of potential by dead resistance would be thirty-six volts and the potential at the arc would be lowered to seventy-four volts. From this we can readily understand the performance of the dead resistance in effecting stability of current by causing a varying supply of potential at the are directly inversely to the variation of current passing to meet the requirements of the are.

Now it is the purpose of this invention to perform the function of the dead resistance by operating magnetically a variable or live resistance in the arc-circuit in such a manner as to have definite resistances in relation to variations of current. For instance, the resistance should be three ohms when the current is at the normal amount of five amperes, taking up fifteen volts drop of potential, and with a constant potential at the mains of ninety-five volts, leaving eighty volts potential at the are. lVith a fall of current to four amperes the resistance should be two and on efourth ohms, taking up nine volts drop of potential out of the ninety-five at the mains and leaving eighty-six at the arc. lVith a rise of current to six amperes the resistance should be three and one-half ohms, taking up twenty-one volts drop of potential out of the ninety-five at the mains and leaving seventyfour at the are. In this manner the performance of the dead resistance can be effected with a mean drop of potential at the live resistance of about fifteen volts instead of the thirty necessitated by the dead resistance. In other words, the dead resistance will consume one hundred and fifty watts of electrical energy, while the live. resistance which forms the subject of my present invention will consume only about seventy-five watts, for the condition of stability.

In the accompanying drawings, Figure 1 represents diagramatically a simple form of arc-lamp embodying my invention, and Fig. 2 is a diagram illustrative of my invention.

In Fig. 1, B is the upper or movable carbon electrode, carried by a tapered solenoidcore S, acted upon magnetically by a solenoid-coil Q in the arc-circuit. D is the lower or fixed carbon electrode, M an arc-inclosing globe, and P is a dash-pot to dampen the movement of the core S. These parts consitute a simple known form of arc-lamp. My invention is represented by a live resistance R, composed of carbon plates under pressure of a weight \V, connected to a solenoid-core I, acted upon magnetically by a solenoid-coil K in the arceircuit to vary the pressure upon the carbon plates, and therefore the resistance of R, in accordance with my invention. The flow of current in the circuit is indicated by arrowheads, and X Y represent the lamp-terminals for the line connections. In order that this form of lamp will regulate for a mean current of five amperes, the number of wire turns in the solenoid coil Q, should be of such an amount as to just be able to lift the core S and carbon 13 when five amperes are passing, andin order thatthe live resistance will effect stability of current with a mean potential voltage at the are of eighty volts and a constant voltage at the mains of ninety-live volts the number of wire turns in the solenoid-coil K should be of such an amount in relation to the weight W as to make the resistance of It about three ohms when the current passing is five ainperes, while at the same time the amount of wire turns in coil K and size of weight \V should be such that a fall of current to four amperes will act to make the resistance of R about two and one-fourth ohms, while a rise of current to, say, six ainperes will make it about three and one-half ohms resistance or slightly more. The larger the size of coil K and weight \V the greater, of course, will be the variation of resistance in relation to the current, so that the proper variation of resistance in relation to the current can be determined by the size of coil K and weight \V, while the mean resistance can be determined by the relative sizes of coil K and weight \V. The operation of this form of means in effecting the purpose of this invention will be obvious, for it will be seen that coil Q of the lamp will act to regulate the current at the desired mean amount and that the live resistance will effect a varying supply of potential at the are directly inversely to the variation of current to meet the requirements of the are herein pointed out. It is not to be in ferrcd, however, that any form of variable resistance could be so adjusted and act to meet the requirements of the arc. li o r instance, a sliding-contact form of variable resistance would require too much movement for the working parts and in consequence of resultant inertia and friction would be more apt to effect instability than stability.

.3y the carbon form of live resistance shown in the drawings there is practically no movement nor friction to the working parts, and I have been able to effect stability with same without difficulty.

In the diagram Fig. 2 l have graphically shown the performance of the carbon form of live resistance as more nearly obtained in practice by the line H, the potential voltage being laid off along the ordinates and the current amperage along the abscissas. The mark N represents the normal or mean working drop of potential at the arc and amount of current passing. The line 0 represents the performance of dead resistance, the constant potential voltage at the mains in each respective case being indicated byline C and line H on the ordinate of zero current. It will be seen that line C and line H are approximately parallel near the mark N and that both performances would meet the requirements of the are for ordinary working variations of current from the normal or mean amount, while at the same time it willbe seen that line C leads to one hundred and ten volts at the mains and line H leads to ninety-five volts, and therefore necessitates the curved form of line H. New this curved form of line H is incidentally the performance of the carbon form of live resistance without special means, and it is owing to the inherent nature of a variable carbon resistance that its resistance varies in a greater inverse ratio to the ance is particularly applicable for carrying out the object of this invention.

I am aware that a variable resistance has been used in connection with arc-lamps to compensate for variations of potential at the mains, such as railway-circuits subjected to varying loads; but such means are for regulation, and act to effect a constant-potential supply from a varying potential at the mains, while my invention'is for stability, and acts to effect a varying-potential supply from a constant potential at the mains.

It will be of course apparent that other po tential voltages and currents than those here in referred to could be used in connection With my invention, and that other than the precise form of arc-lamp and construction means herein shown and described could be used without departing from the scope of my invention.

I claim as my invention 1. The method herein described of effecting stability of current for an electric-arc lamp, taking current from direct-current constantpotential mains, said mode consisting of effecting a varying supply of potential at the are inversely to variations of current, by magnetically operating a variable resistance in the arc-circuit to vary the resistance of same with the variation of current, substantially as and for the purpose described.

2. An electric-arc lamp for direct-current constant-potential circuits,provided with suitable magnetic means for maintaining the desired mean amount of current passing, in combination with independent magnetic means in the arc-circuit, and a Variable resistance operated upon by said independent magnetic means to eifect a varying potential at the are inversely to variations of current to meet the requirements of the are for stability of current, substantially as described.

3. An electric-arc lamp for direct-current constant-potential circuits provided with suitable magnetic means for maintaining the current passing at the desired mean amount, in combination with independent magnetic means in the arc-circuit, and a carbon-plate resistance operated on by said independent magnetic means to vary pressure upon the carbon plates and so Vary the resistance of same with the variation of current, and there by effect a varying potential at the arc inversely to the variation of current passing, substantially as and for the purpose described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

DANIEL IIIGIIAM.

\Vitnesses:

ALPHONSO A. WYMAN, ARTHUR O. SHAFTER. 

